I’m sure you can understand that insurance is a good idea to have. I would also advise to check what is covered, especially in regards to winter sports and what they consider on and off piste. If you don’t have insurance you can by it with your liftpass for a few Euros a day or you can go direct to Assuren sport and get the same insurance that covers multiple extreme sports for £79 for the year. Once you have your insurance make sure you keep the details of it with you. Should anything happen, the rescue services will be a lot easier to deal with if you can show proof of your insurance.
For other medical requirements it’s worth being aware of the differences in the health system compared to the UK. Primarily in that it is not completely free and a lot of doctors surgeries are private (including the one in Morzine). If you take yourself to the doctor you will need to pay for the consultation and any subsequent prescriptions or equipment. If you are in such a situation that you are taken straight to hospital you may receive a bill after. If you have your GHIC card (which I would thoroughly recommend), then you will be treated in the same way as nationals. Which is you will need to pay about 20%.